A machine controls interface. Cincinatti Milacron Xtreem St HMI. They said the LCD screen has a backlight, but nothing else! I connect my external monitor to the controller’s video-out to verify that the issue is indeed not the video / I/O card:
Hmm. So the problem is video signal cable or LCD. That’s a very proprietary LVDS ribbon there. I etched / deox-id / dielectric grease all connections, reworked finicky ribbon solder work at LCD panel, pull and verify a few components on board…The display has a variable potentiometer “Contrast” adjustment ribbon. A little care to that: and totally rework power supply traces that are almost entirely corroded away, reassemble: it WORKS! NEXT!
Who’s the idiot that said “NEXT!”? They brought yet another one. This next one does not respond to keypad input. I had a wife like that, once. Maybe I’ll have better results asking a machine control why it doesn’t taste like beer yet…
And Milwaukee Mac Repair / Industrial Power & Microelectronics, L.L.C. fixes yet another misbehaving machine control. NEXT! oh. Another one arrives. Is the dead. A bailing machine has developed an attitude problem. What ails you SON!? Oh, you just got a little corrosion here and there – lemme clean that up a little bit – AAAaaand there, you should be all good as new now!
Aint dead no mo! MOAR!
Complaint here was that unknown unfamiliar arbitrary random board “not driving LCD”. – They had swapped boards and the other board worked. I had NO clue what this thing was from, how it connects to anything, which end was up…COOL! It’s electronics repair! Reverse-engineer it! Board had some AC power inputs that (according to connected component values) – looked to want less than 30VAC. The board also had a 24VDC input header. Resistance reading at DC input looked to be a short circuit! I was being trolled by a zener diode. Ohm’s law says it’s fine…DC input capacitor and that diode got pulled from the board and very suspiciously scrutinized and found to be good. I put them back. The five voltage regulators in this picture were all bad! They were fed by a full wave bridge rectifier and some filter caps from the AC supply feeds. I suspected that what had happened to these voltage regulators was that the AC feed step-down transformer(s) passed a power line spike into them. This is why they make Metal Oxide Varistors. Not every engineer has your best interest at heart. Sometimes budget is the only concern. I sent the board back to the customer and they called and told me I can invoice them for it because it worked. Honestly, I had no clue! It only made sense to me that it *should* now work after my repairs.